JP6015899B2 - Paper conveying apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet conveying device and an image forming apparatus.

  Some image forming apparatuses such as copiers, printers, facsimiles, and the like are provided with a paper conveyance path in the vicinity of the transfer roller that can be opened in order to facilitate jam processing at the transfer roller portion.

  For example, Patent Document 1 (Japanese Patent Laid-Open No. 2011-85815), Patent Document 2 (Japanese Patent Laid-Open No. 2004-20574), and Patent Document 3 (Japanese Patent Laid-Open No. 2000-231321 (Japanese Patent No. 3670153)) disclose image formation. A transfer cover can be opened and closed on the side surface of the apparatus body, a transfer roller can be provided on the inner surface of the transfer cover (Patent Documents 1 and 2), and not only the transfer roller but also one roller of the timing roller pair (Patent Document 3).

  Further, as disclosed in Patent Document 4 (Japanese Patent Laid-Open No. 2002-127528), a conveyance frame that can be moved up and down in a swinging manner with respect to the photosensitive drum is provided, and the photosensitive drum is brought into contact with and separated from the photosensitive drum. And a transfer roller for guiding a sheet in a lateral direction with a sheet sandwiched from above and below toward a transfer nip portion between the transfer roller and the photosensitive drum.

  Patent Documents 1 to 3 open the transfer cover to open the paper conveyance path to perform jam processing. Patent Document 4 lowers the conveyance frame to separate the transfer roller from the photosensitive drum and opens the upper and lower transfer guides to jam. Processing is performed.

  If a transfer roller or a timing driving roller is provided on the inner surface of the transfer cover as in Patent Documents 1 to 3, jamming when a sheet is caught on these rollers becomes easy. However, a pair of sheet conveyance guides for guiding both the front and back sides of the sheet are disposed before and after the roller (upstream and downstream in the sheet conveyance direction), and the pair of sheet conveyance guides is usually provided on the main body side. There are many. Therefore, when a paper jam occurs in the paper conveyance guide, there is a problem that the jammed paper cannot be easily removed even if the transfer roller and the timing driving roller are opened together with the transfer cover. Therefore, it may be possible to further facilitate the jam processing by disposing one of the pair of paper transport guides on the transfer cover. In this case, the paper transport guide, the transfer roller disposed on the transfer cover, and the timing are considered. Positioning with the drive roller becomes a problem.

  As in Patent Documents 1 and 2, if a roller on the transfer cover side is provided so as to be swingable, and the movement trajectory when the roller moves as the transfer cover opens and closes is regulated by a predetermined guide, the roller is moved to the main body side. By narrowing the area that interferes with the parts, it is possible to reduce the size and space of the apparatus. However, if the paper transport guide and the roller are arranged on the transfer cover side with a gap so as not to interfere with each other, the counterpart paper transport guide on the main body side must also be disposed apart from the main body side roller. As a result, the advantages of narrowing the roller interference area as described above are diminished, making it difficult to reduce the size and space of the apparatus.

  When the roller is fixedly arranged on the transfer cover as in Patent Document 3, the clearance between the paper transport guide on the transfer cover side and the roller is minimal, but the movement path of the roller when the transfer cover is opened and closed is the same as that of the transfer cover. Therefore, it is difficult to reduce the size and space of the apparatus.

  In the case of Patent Document 4, the transfer roller and the upper transfer guide are disposed so as to be swingable, but the lower transfer guide is fixedly disposed on the transport frame, and an interference area with the main body-side parts as the transport frame moves up and down. No particular consideration is given to the reduction or the space saving of the apparatus.

  In view of the above problems, an object of the present invention is to provide a paper transport device that is not only excellent in paper jam handling performance but also excellent in paper transport performance while being small and space-saving.

  In order to solve the above-described problem, the present invention provides a sheet conveying apparatus having one or more pairs of feeding members that convey a sheet with a sheet interposed therebetween along a sheet conveying path, and opens and closes a part of the sheet conveying path. A cover disposed on a side surface of the apparatus main body so as to cover the body, a body-side feeding member disposed on the body side as one of the pair of feeding members, and the other of the pair of feeding members. A cover-side feeding member arranged to be position-changeable with respect to the cover, a guide member arranged on the main body side for guiding the cover-side feeding member in accordance with the opening / closing operation of the cover, and the cover side A sheet conveying apparatus including a sheet conveying guide that is disposed on the upstream side or the downstream side of the feeding member so that the position of the feeding member can be changed and is engaged with the cover-side feeding member so as to be interlocked with the cover-side feeding member.

  According to the present invention, the cover-side feeding member is disposed so as to be movable by the main body-side guide member in accordance with the cover opening / closing operation, and the cover-side paper conveyance guide is engaged with the cover-side feeding member in an interlockable manner. Further, it is possible to improve the jam handling property of the paper caught on the feeding member and the paper conveyance guide. Further, an area that does not interfere with the movement trajectory of the cover-side feed member in the vicinity of the main body-side feed member can be increased, and the feed member and the paper transport guide are arranged close to each other on the cover side by an interlocking structure. Thus, it is possible to reduce the size and space of the apparatus. Further, it is possible to improve the sheet conveying property by the close arrangement of the feeding member and the sheet conveying guide on the cover side.

1 is a perspective view of an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view illustrating an internal structure of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a perspective view of the image forming apparatus according to the embodiment of the present invention with the transfer cover opened. FIG. 3 is a cross-sectional view of the image forming apparatus according to the embodiment of the present invention with the transfer cover opened. It is a perspective view which shows the inner side state of a transfer cover when a transfer cover is closed. It is a disassembled perspective view which shows the rotating shaft attachment structure of a timing drive roller. FIG. 6 is a perspective view of one end side of a timing driving roller and a sheet conveyance guide. It is a perspective view of the other end side of a timing drive roller and a paper conveyance guide. FIG. 4 is a side view of one end side of a timing driving roller and a sheet conveyance guide. It is a side view of a paper conveyance guide, a rotation arm, and a support member. It is a side view of a paper conveyance guide, a rotation arm, and a support member. It is a side view of a paper conveyance guide, a rotation arm, and a support member. It is a side view of a paper conveyance guide, a rotation arm, and a support member. FIG. 6 is a perspective view of a timing driven roller and a sheet conveyance guide. FIG. 6 is a perspective view of one end side of a timing driven roller and a sheet conveyance guide. It is a side view of a positioning guide member. FIG. 9 is a side view showing a state immediately before the rotation shaft of the timing drive roller is guided by the positioning guide member in the final first stage of closing the transfer cover. FIG. 10 is a side view showing a state in which the rotation shaft of the timing driving roller is being guided by the positioning guide member in the final second stage of closing the transfer cover. FIG. 10 is a side view showing a state in which the timing driving roller is in contact with the timing driven roller in the final third stage of closing the transfer cover. It is a figure which shows the movement locus | trajectory of the timing drive roller at the time of transfer cover opening and closing. It is a perspective view which shows the state of the timing drive roller in the cover inner surface when a transfer cover is opened. It is a perspective view which shows the state of the timing drive roller in the cover inner surface when a transfer cover is closed. FIG. 6 is a perspective view showing a state of a sheet conveyance guide on the inner surface of the cover when the transfer cover is closed. FIG. 6 is a perspective view showing a relative relationship between a timing driving roller and a transfer roller on the inner surface of the cover when the transfer cover is closed. FIG. 6 is a perspective view showing a relative relationship between a timing driving roller and a transfer roller on the inner surface of the cover when the transfer cover is opened. It is sectional drawing of the image forming apparatus which shows the modification of this invention.

  Hereinafter, an image forming apparatus including a sheet conveying device according to an embodiment of the present invention will be described with reference to the drawings.

  In the present application, “image forming apparatus” refers to an apparatus that forms an image by attaching a developer or ink to a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, or the like. means. “Image formation” means not only giving an image having a meaning such as a character or a figure to a medium but also giving an image having no meaning such as a pattern to the medium. “Paper” is not limited to paper, but includes the above-described OHP sheet, cloth, and the like, and means that a developer or ink adheres to the recording medium, recording medium, recording paper, recording paper. It is used as a general term for things including what is called.

(Image forming device)
FIG. 1 is an external perspective view of a laser printer as an image forming apparatus provided with a sheet conveying device according to an embodiment of the present invention. The image forming apparatus to which the paper conveying apparatus according to the present invention is applied may be a copying machine, a printer, or a facsimile machine, or may be a complex machine that combines two or more of these. A paper feed tray 30 is disposed at the lower part of the image forming apparatus, and a transfer cover 8 serving as an internal inspection cover is disposed above the paper feed tray 30. A paper discharge tray 44 is disposed at the top of the apparatus.

  The transfer cover 8 includes a double-side unit 9 on the inner surface thereof, and as shown in FIG. 2, the transfer cover 8 can be rotated to the front side of the image forming apparatus around a rotation shaft 12 disposed at the lower part of the apparatus. FIG. 3 shows a state in which the transfer cover 8 is opened to the front side.

  The duplex unit 9 has a transport housing 9a, and a paper return path 9b is formed on the back side of the transport housing 9a. Further, the inner surface side of the transport housing 9 a constitutes a part of the sheet transport path on the main body side, and includes a secondary transfer roller 20 as a transfer member and one timing driving roller 32 a of the timing roller pair 32. . The secondary transfer roller 20 constitutes a pair of transfer rollers as a pair of feeding members with a drive roller 18 on the main body side to be described later, and the pair of timing drive rollers 32a with a timing driven roller 32b on the main body side. The timing roller pair 32 is configured as a feed member.

  The main part of the image forming apparatus will be described below with reference to FIG. The image forming apparatus includes four process units 1K, 1Y, 1M, and 1C as image forming units that form images with developers of black, yellow, magenta, and cyan corresponding to color separation components of a color image. .

  Process units 1K, 1Y, 1M, and 1C are arranged on the main body side of the image forming apparatus. Each process unit 1K, 1Y, 1M, 1C has toner bottles 6K, 6Y, 6M, 6C containing unused toners of different colors. Other than that, the configuration is the same. The structure of one process unit 1K will be described as an example. The process unit 1K includes an image carrier 2K (photosensitive drum), a drum cleaning device 3K, a static eliminator (not shown), a charging device 4K, a developing device 5K, and the like. Have. The process unit 1K is detachably attached to the main body of the image forming apparatus, so that consumable parts can be replaced at a time.

  An exposure unit 7 is disposed above each process unit 1K, 1Y, 1M, 1C. The exposure device 7 is configured to emit laser light from a laser diode based on image data.

  A transfer device 15 serving as a first transfer unit is disposed below each process unit 1K, 1Y, 1M, 1C. The transfer device 15 includes four primary transfer rollers 19K, 19Y, 19M, and 19C facing each image carrier 2K, 2Y, 2M, and 2C, each primary transfer roller 19K, 19Y, 19M, and 19C, a driving roller 18, and a driven roller. 17 includes an intermediate transfer belt 16 that circulates around 17, a secondary transfer roller 20 as a second transfer unit disposed opposite to the driving roller 18, a belt cleaning device 21, a cleaning backup roller 22, and the like. If the image carriers 2K, 2Y, 2M, and 2C are the first image carriers of the respective colors, the intermediate transfer belt 16 is a second image carrier that combines these images.

  At the bottom of the image forming apparatus, there are provided a paper feed tray 30 that can accommodate a large number of paper P and a paper feed roller 30 a that feeds the paper P from the paper feed tray 30 toward the paper feed path 31. Near the end of the paper feed path 31, a timing roller pair 32 for temporarily stopping the paper is provided. The timing roller pair 32 is located immediately upstream of the intermediate transfer belt 16, and in order to accurately align the toner image on the intermediate transfer belt 16 and the leading edge position of the sheet, the sheet P is once slackened to perform intermediate transfer. Immediately before the toner image formed on the belt 16 is transferred to the paper P at the secondary transfer nip portion, the paper P is sent to the secondary transfer nip portion at a predetermined timing.

  In general, the secondary transfer roller 20 is often urged to the intermediate transfer belt 16 by a compression spring 25. However, in the full-front operation type image forming apparatus, the duplex unit 9 is often disposed on the front side of the intermediate transfer belt 16, and it is difficult to make the periphery of the compression spring 25 compact. Therefore, as shown in FIG. 2, when the transfer nip portion is arranged in an oblique direction, the dead space of the duplex unit 9 can be used effectively, and the compactness of the image forming apparatus in the front-rear direction can be achieved.

  A post-transfer conveyance path 33 is disposed above the nip portion between the secondary transfer roller 20 and the driving roller 18. Near the end of the post-transfer conveyance path 33, a fixing device 34 as a fixing unit is provided. The fixing device 34 includes a fixing roller 34a containing a heat source such as a halogen lamp (not shown), and a pressure roller 34b that rotates while contacting the fixing roller 34a with a predetermined pressure.

  A post-fixing conveyance path 35 is disposed above the fixing device 34, and branches to a paper discharge path 36 and a reverse conveyance path 41 at the end of the post-fixing conveyance path 35. A switching member 42 that swings around a swing shaft 42a is disposed on the side of the post-fixing conveyance path 35. A paper discharge roller pair 37 is disposed at the end of the paper discharge path 36. The reverse conveyance path 41 joins the paper feed path 31 at the end thereof, and a reverse conveyance roller pair 43 is disposed in the middle of the reverse conveyance path 41. A paper discharge tray 44 having an upper cover recessed inward is disposed at the top of the image forming apparatus.

  A powder container 10 (toner container) for storing waste toner is disposed between the transfer device 15 and the paper feed tray 30. The powder container 10 is detachably attached to the image forming apparatus main body.

  In the image forming apparatus of this embodiment, the space from the paper feed roller 30a to the secondary transfer roller 20 needs to be separated to some extent due to the transfer paper transfer relationship. For this reason, the powder container 10 is installed in the dead space generated to reduce the size and space of the entire image forming apparatus.

(Operation of image forming apparatus)
Next, the basic operation of this image forming apparatus will be described. In FIG. 1, when a paper feed roller 30 a is rotated by a paper feed signal from a control unit of an image forming apparatus (not shown), only the topmost paper P stacked on the paper feed tray 30 is separated and fed to the paper feed path 31. Sent out. When the leading edge of the paper P reaches the nip portion of the timing roller pair 32, the timing is synchronized with the toner image formed on the intermediate transfer belt 16, and the paper P is slackened to correct the skew of the leading edge of the paper P. Wait in the state of forming.

  The image forming operation will be described by taking one process unit 1K as an example. First, the charging device 4K charges the surface of the image carrier 2K to a uniform high potential. Based on the image data, the exposure device 7 irradiates the surface of the image carrier 2K with the laser beam L, and the potential of the irradiated portion is lowered to form an electrostatic latent image. Unused black toner is supplied from the toner bottle 6K to the developing device 5K.

  The toner is transferred to the surface portion of the image carrier 2K on which the electrostatic latent image is formed by the developing device 5K, and a black toner image is formed (developed). Then, the toner image formed on the image carrier 2K is transferred to the intermediate transfer belt 16.

  The drum cleaning device 3K removes residual toner adhering to the surface of the image carrier 2K after the intermediate transfer process. The removed residual toner is sent to a waste toner container in the process unit 1K and collected by a waste toner transport unit (not shown). Further, a static elimination device (not shown) neutralizes residual charges on the image carrier 2K after cleaning.

  In the process units 1Y, 1M, and 1C for the respective colors, toner images are similarly formed on the image carriers 2Y, 2M, and 2C, and the respective color toner images are transferred to the intermediate transfer belt 16 so as to overlap each other.

  When the color toner images are transferred to the intermediate transfer belt 16 so as to overlap each other, the timing roller pair 32 and the paper feed roller 30a start driving, and take timing (synchronization) with the toner image superimposed and transferred to the intermediate transfer belt 16. The paper P is sent to the secondary transfer roller 20. Then, the toner image on the intermediate transfer belt 16 is transferred to the fed paper P by the secondary transfer nip portion of the secondary transfer roller 20.

  The paper P to which the toner image has been transferred is conveyed to the fixing device 34 through the post-transfer conveyance path 33. The paper P sent to the fixing device 34 is sandwiched between the fixing roller 34a and the pressure roller 34b, and the unfixed toner image is heated and pressed to be fixed on the paper P. The sheet P on which the toner image is fixed is sent out from the fixing device 34 to the post-fixing conveyance path 35.

  At the timing when the paper P is sent out from the fixing device 34, the switching member 42 is at the position indicated by the solid line in FIG. 1 and opens near the end of the post-fixing conveyance path 35. The paper P sent out from the fixing device 34 passes through the post-fixing conveyance path 35, is sandwiched between the paper discharge roller pair 37, and is discharged to the paper discharge tray 44.

  When performing duplex printing, when the trailing edge of the paper P conveyed by the paper discharge roller pair 37 passes through the post-fixing conveyance path 35, the switching member 42 swings to the position indicated by the dotted line in FIG. The vicinity of the end of the path 35 is closed. At substantially the same time, the paper discharge roller pair 37 rotates in the reverse direction, and the paper P is fed back and enters the reverse conveyance path 41.

  The sheet P transported in the reverse transport path 41 passes through the reverse transport roller pair 43, reaches the timing roller pair 32, and is sent out in synchronism with the toner image for the back surface formed on the intermediate transfer belt 16. A toner image is transferred to the back surface of the paper P when passing through the secondary transfer roller 20. After the toner image on the back surface of the paper P is fixed by the fixing device 34, the toner image is discharged to the paper discharge tray 44 through the post-fixing conveyance path 35, the paper discharge path 36, and the paper discharge roller pair 37 in order.

  Further, after the toner image on the intermediate transfer belt 16 is transferred to the paper P, residual toner adheres on the intermediate transfer belt 16. This residual toner is removed from the intermediate transfer belt 16 by the belt cleaning device 21.

  The toner removed from the intermediate transfer belt 16 is collected in the powder container 10 by a waste toner conveying means (not shown) (see FIG. 2).

(Transfer cover)
When a jam occurs due to a paper jam during printing, as shown in FIGS. 3 and 4, the user can open the transfer cover 8 outward with the rotation shaft 12 as a center and take out the jammed paper. When the paper P is sandwiched between the timing roller pair 32, the pressure of the timing roller pair 32 is very high, so that it is difficult to take out jammed paper while the timing roller pair 32 is closed.

  In this embodiment, the transfer roller 20 and one timing drive roller 32a of the timing roller pair 32 are disposed inside the transfer cover 8, and the transfer roller 20 and the timing roller are opened by opening the transfer cover 8. The pair 32 can be opened at the same time, and the jam processing can be performed quickly and easily. That is, as shown in FIGS. 3 and 4, when the transfer cover 8 is released to the front side with the rotary shaft 12 as the center, the fixing device 34, the end of the intermediate transfer belt 16, the timing driven roller 32 b, etc. Since it can be seen, the internal jam processing is easy.

(Secondary transfer roller)
The secondary transfer roller 20 is disposed inside the transfer cover 8 as shown in FIGS. 12A to 12C. On the inner surface of the transfer cover 8, a pair of end plates 27 are fixed to the left and right side portions by a plurality of screws 29, whereby each unit such as the secondary transfer roller 20 and the timing drive roller 32 a attached to the end plate 27 is provided. This contributes to improving the strength of the transfer cover 8. A support plate 28 is disposed inside the end plate 27, and the rotation shaft 20 a of the secondary transfer roller 20 is rotatably supported on the support plate 28. As shown in FIG. 2, the support plate 28 is urged toward the secondary transfer driving roller 18 by a compression spring 25.

(Timing drive roller)
As shown in FIG. 5, both ends of the rotation shaft 32a1 of the timing drive roller 32a disposed on the inner surface of the transfer cover 8 are supported by the rotating arm 45 in a state of protruding slightly outward in the axial direction ( The transfer roller 20 is not shown). The pivot arm 45 is inserted into an elongated hole 45a formed at the base end thereof so that the support shafts 27a of the end plates 27 on both sides of the transport housing 9a can be rotated. And can be slid in the direction of the elongated hole 45a. The end of the rotating shaft 32a1 of the timing drive roller 32a is rotatably inserted into the shaft hole 45b at the tip of the rotating arm 45. The timing drive roller 32a is rotationally driven in both forward and reverse directions by a rotational drive mechanism (not shown).

  In addition, since the inner peripheral surface of the shaft hole 45b is in direct contact with the rotating shaft 32a1 of the timing driving roller 32a, the rotating arm 45 has a good slidability with the rotating shaft 32a1. It is good to. In addition, it is desirable that the rotating arm 45 has a symmetrical shape in order to reduce the number of parts and improve the assemblability by sharing the left and right sides.

  As shown in FIG. 6, a pressure lever 46 is disposed between the rotating arm 45 and the end plate 27. The pressure lever 46 has a shaft hole 46a formed at an intermediate position in the length direction, and a support shaft 27b formed on the end plate 27 is inserted into the shaft hole 46a. The pressure lever 46 is rotatable about the support shaft 27b.

  As shown in FIGS. 12A to 12C, one end of a tension spring 47 as an elastic member is connected to the hook portion 46 b at the lower end portion of the pressure lever 46. The other end of the tension spring 47 is hooked on the shaft 27 c of the end plate 27. The pressure lever 46 is always urged to rotate in the direction of the arrow (counterclockwise) about the support shaft 27b by the tension spring 47.

  The side surface of the tip of the pressure lever 46 forms a flat pressing surface 46c, and this pressing surface 46c is formed around the shaft hole 45b of the rotating arm 45 by the force of the tension spring 47 as shown in FIGS. It abuts against the formed pressed surface portion 45c. The rotating arm 45 is always pressed from the direction of the rotation shaft 32b1 of the timing driven roller 32b, that is, from the support shaft 27a as shown by the arrow direction when the transfer cover 8 is closed by pressing the pressed surface portion 45c. It is the direction which leaves | separates and is urged | biased by rotation counterclockwise by FIG. 12C centering on the spindle 27a.

  The elongated hole 45a of the rotating arm 45 enables the rotating arm 45 to move in the direction of the arrow by the force of the tension spring 47. The spring for urging the rotating arm 45 is not limited to the tension spring 47. Instead of the pressure lever 46 and the tension spring 47, a torsion spring that urges counterclockwise around the support shaft 27a is disposed, and a rotating arm 45 is provided on the left side of the support shaft 27a in the elongated hole 45a. An urging action equivalent to the above can also be obtained by disposing a compression spring that urges outward.

  A stopper 48 is formed in the vicinity of the spring hook shaft 27c of the end plate 27 as shown in FIGS. The stopper 48 is formed by cutting and raising the end plate 27, and when the transfer cover 8 is opened, the pressure lever 46 abuts against the stopper 48 to restrict its counterclockwise rotation position. By restricting the rotation range of the pressure lever 46 to the necessary minimum by the stopper 48, the layout of the components around the pressure lever 46 is given a margin, and the amount of expansion and contraction of the tension spring 47 is minimized. Reduce costs. When the transfer cover 8 is closed, the pressure lever 46 is separated from the stopper 48, and a predetermined gap S1 is formed between them.

  The rotational moment of the pressure lever 46 is determined by the ratio (lever ratio) of the distance from the hook portion 46b of the tension spring 47 to the support shaft 27b and the distance from the support shaft 27b to the pressing surface 46c. In this embodiment, the force of the tension spring 47 is increased several times by the lever ratio of the distance and is transmitted to the pressed surface portion 45 c of the rotating arm 45. Therefore, even with a small spring force of the tension spring 47, a large timing roller nip pressure can be generated, so that the necessary timing roller nip pressure can be obtained with a compact and small tension spring 47.

  As described above, the hole shape in which the support shaft 27a of the end plate 27 is inserted into the rotating arm 45 is the long hole 45a, so that the rotation is performed by the gap between the long hole 45a and the support shaft 27a. The moving arm 45 is movable in the longitudinal direction. By doing so, the timing driving roller 32a can be stably pressed against the timing driven roller 32b, and a stable timing roller nip pressure can be secured. The relationship between the long hole 45a and the support shaft 27a can be reversed. That is, by inserting the support shaft formed at the base end portion of the rotating arm 45 into the elongated hole formed in the end plate 27, the same operation as described above can be obtained.

  When the transfer cover 8 is opened, that is, when an external force is not applied to the outer peripheral surface of the timing driving roller 32a, the rotating arm 45 is at its lowest position as shown in FIGS. It is rotating sideways or counterclockwise. The rotating arm 45 is in contact with the stopper surface 52b at the upper end of the support member 52 described later by its own weight.

  In this state, that is, in the state shown in FIG. 12A, the rotating arm 45 can freely move by the gap in the elongated hole 45a existing on the left and right of the support shaft 27a. On the other hand, the pressure lever 46 is rotated to the counterclockwise limit by the force of the tension spring 47 and is in contact with the stopper 48. Therefore, the rotating arm 45 and the pressure lever 46 are separated from each other, and a gap S2 is formed between them.

(Paper transport guide)
As shown in FIGS. 7A to 7C, a sheet conveyance guide 50 of the duplex unit 9 is disposed below the timing driving roller 32a. The sheet conveyance guide 50 is for accurately guiding the sheet conveyed to the timing roller pair 32 to the transfer nip portion, and a similar sheet conveyance guide 51 is also provided on the main body side as shown in FIG. Is arranged.

  In the conventional image forming apparatus, the sheet conveyance guide 50 is fixedly disposed on the inner surface of the conveyance housing 9a. In the embodiment of the present invention, the timing driving roller 32a is movably disposed with respect to the transport housing 9a. Therefore, if the sheet transport guide 50 is fixedly disposed as in the prior art, the timing drive roller 32a is disposed. May interfere with the paper transport guide 50.

  In addition, if the paper conveyance guide 50 is arranged sufficiently apart from the timing driving roller 32a so that such interference does not occur, the gap between the timing driving roller 32a and the paper conveyance guide 50 becomes too large. As a result, it becomes difficult to stably guide the paper to the timing roller nip portion, and the possibility of paper jam due to the large gap increases.

  Therefore, in the embodiment of the present invention, the sheet conveyance guide 50 is configured to be movable together with the timing driving roller 32a. As shown in FIG. 7C, a bearing portion 50a is formed at the upper end portion of the sheet conveyance guide 50, and this bearing portion 50a is rotatably engaged with the rotation shaft 32a1 of the timing drive roller 32a. The bearing portion 50a is formed with a notch 50a1 in a part thereof to form a C shape in a side view, and the rotation shaft 32a1 of the timing drive roller 32a can be easily clicked sideways (in the radial direction) from the notch. Engageable. The periphery of the bearing portion 50a is formed in an arcuate surface 50e centered on the rotation shaft 32a1.

  The width of the notch 50a1 is formed slightly smaller than the diameter of the rotary shaft 32a1, and once the rotary shaft 32a1 is inserted into the bearing 50a from the notch 50a1, the rotary shaft 32a1 is stably supported by the bearing 50a. It has a structure. The notch 50a1 can also be formed on the left side of the paper transport guide 50 in FIG. 7C. As described above, since the paper transport guide 50 can be easily attached to the rotary shaft 32a1, the cost of the apparatus can be reduced by improving the assembling workability, and the paper transport guide 50 can be replaced or maintained when the paper transport guide 50 is damaged or soiled. Easy.

  In this way, by engaging the bearing portion 50a of the paper conveyance guide 50 with the rotation shaft 32a1 of the timing driving roller 32a, the bearing portion 50a of the paper conveyance guide 50, that is, the downstream end of the paper conveyance guide 50, together with the timing driving roller 32a. It can be moved. Therefore, the gap between the downstream end of the sheet conveyance guide 50 and the timing driving roller 32a can be always maintained at a predetermined minimum gap. Accordingly, it is possible to stably feed the sheet to the timing roller nip portion, and it is possible to prevent the sheet from getting into the gap and causing the sheet jam. In addition, the sheet conveyance guide 50 can be configured with the minimum dimensions indispensable for the conveyance immediately before the timing roller pair 32, so that the apparatus can be reduced in size, space and cost.

  As shown in FIG. 7A, a short-axis boss portion 50b is integrally formed at the lower end portion (upstream end portion) of both end faces of the sheet conveyance guide 50. On the other hand, as shown in FIGS. 7A and 7B, a support member 52 that guides the boss portion 50b in the vertical direction is disposed at the lower position of both ends of the rotation shaft 32a1 of the timing drive roller 32a. The support member 52 is fixed to the end plate 27 with screws.

  As shown in FIGS. 7A and 7B, the support member 52 is disposed so that the front half thereof faces both ends of the sheet conveyance guide 50, and a straight vertical groove 52a is formed in a portion facing both ends. Yes. The vertically long groove 52a functions as an engaging portion that guides the boss portion 50b of the paper transport guide 50 so as to be slidable in the vertical direction. The vertical groove 52a has a constant width slightly larger than the diameter of the boss portion 50b and a predetermined length in the vertical direction. It extends in the length. The boss portion 50b of the sheet conveyance guide 50 is slidably engaged with the longitudinal groove 52a, so that the sheet conveyance guide 50 moves when the sheet conveyance guide 50 moves following the movement of the timing drive roller 32a. The position or trajectory of the upstream end is regulated by the longitudinal groove 52a.

  When the vertical groove 52a of the support member 52 is described in more detail functionally, the functions of the left engaging surface 52c and the right engaging surface 52d of the vertical groove 52a are slightly different. The left and right engagement surfaces 52c and 52d do not necessarily have to be configured as a pair, and when either one of the functions is sufficient, the left engagement surface 52c or the right engagement surface 52c or the right engagement surface as shown in FIGS. 8A and 8B. A configuration in which only one of the mating surfaces 52d is disposed is also possible.

  The left engagement surface 52c is formed on the sheet conveyance path S side as viewed from the boss portion 50b in FIG. 8A, and restricts the boss portion 50b from moving to the left side from the engagement surface 52c. Is controlled to be too close to the paper conveyance path indicated by the arrow S. That is, the apparatus can be easily reduced in size and saved in a state in which the necessary minimum gap between the paper transport guide 50 and the paper transport path S is ensured. Further, the degree of freedom of movement of the sheet conveyance guide 50 to the right in FIG. 8A is left, and the sheet conveyance guide 50 is prevented from being damaged when an excessive force is applied to the sheet conveyance guide 50 during sheet conveyance.

  On the other hand, the right engagement surface 52d is formed on the side opposite to the sheet conveyance path S side as viewed from the boss portion 50b in FIG. 8B, and the boss portion 50b is restricted from moving to the right side from the engagement surface 52d. This restricts the paper transport guide 50 from being too far away from the paper transport path S.

  As shown in FIG. 8C, the above functions can be obtained by providing a pair of left and right engaging surfaces 52c and 52d. By preventing the paper transport guide 50 from rattling, the positional variation with respect to the paper transport path S is reduced, and the paper It is possible to prevent the paper conveyance guide 50 from being caught. Further, by preventing the paper transport guide 50 from rattling, the movable range of the guide 50 can be limited (minimum required), and the clearance between adjacent components can be reduced, thereby reducing the size and space of the apparatus. make it easier.

  Further, by making the pair of left and right engaging surfaces 52c and 52d parallel, the movement of the sheet conveying guide 50 in conjunction with the timing driving roller 32a becomes smooth, the opening / closing operability of the transfer cover 8 is improved, and usability is improved and maintenance is performed. It is possible to improve the performance together.

  In this way, on both sides in the width direction of the paper transport guide 50, the boss portions 50b disposed at the lower end (upstream end) are slidably engaged with the longitudinal grooves 52a, and the upper end (downstream end) of the paper transport guide 50 is Since it is engaged with the rotation shaft 32a1 of the timing drive roller 32a, the posture thereof is stabilized in a form in which the four corners of the paper transport guide 50 are supported. The distance between the upper end (downstream end) of the paper transport guide 50 and the timing drive roller 32a is also accurately maintained.

  The longitudinal direction of the engagement surface 52c or 52d of the longitudinal groove 52a may be arranged along the paper transport path S, preferably in parallel with the paper transport path S, as shown in FIGS. 8A to 8C. Thereby, the positional fluctuation of the paper transport guide 50 with respect to the paper transport path S can be reduced so that the paper is not easily caught by the paper transport guide 50. Further, by limiting the movable range of the sheet conveyance guide 50 (required minimum), it is possible to reduce the clearance between adjacent components and facilitate the miniaturization and space saving of the apparatus.

  Further, as shown in FIG. 8D, the longitudinal direction of the engaging surface 52c or 52d of the longitudinal groove 52a is perpendicular to the straight line Q connecting the rotation shafts 32a1 and 32b1 of the timing driving roller 32a and the timing driven roller 32b ( (Vertical) or almost right angle (vertical). As a result, the positional fluctuation of the sheet conveyance guide 50 with respect to the sheet conveyance path (indicated by the straight line P in FIG. 8D) can be reduced, and the sheet can be prevented from being caught by the sheet conveyance guide 50.

  That is, it is possible to ensure that the leading edge of the sheet enters from the front side with respect to the nip portion formed between the timing roller pair 32. Further, by limiting the movable range of the sheet conveyance guide 50 (required minimum), it is possible to reduce the clearance between adjacent components and facilitate the miniaturization and space saving of the apparatus.

  Further, the longitudinal direction of the engagement surface 52c or 52d of the longitudinal groove 52a is perpendicular (perpendicular) or substantially perpendicular to the pressing direction of the timing driving roller 32a against the timing driven roller 32b (indicated by the arrow R in FIG. 8D). (Vertical) can also reduce the positional fluctuation of the sheet conveyance guide 50 with respect to the sheet conveyance path P and make it difficult for the sheet to be caught by the sheet conveyance guide 50 as described above. In addition, by making the pressing direction R of the timing drive roller 32a coincide with the direction of the straight line Q, it is possible to further increase the difficulty of catching the paper. Further, by limiting the position variation or movable range of the sheet conveyance guide 50 (required minimum), it is possible to reduce the clearance between adjacent components and facilitate further downsizing and space saving of the apparatus.

  As shown in FIG. 8, the support member 52 is positioned below the rotating arm 45, and the upper end of the support member 52 forms a flat stopper surface 52b. The stopper surface 52b is configured such that the lower surface of the rotating arm 45 can come into contact therewith, and when the rotating arm 45 is rotated downward by the force of the tension spring 47, the rotating arm 45 is The support member 52 comes into contact with the stopper surface 52b.

  The stopper surface 52 b is not necessarily formed on the support member 52, and the stopper surface 52 b can be formed on a portion that is separated from the support member 52 and cut and raised from the end plate 27. However, it is desirable to form the stopper surface 52b on the support member 52 as much as possible in order to reduce the size and space.

  When the user opens the transfer cover 8 for a certain period of time, such as during paper jam processing, the user can contact the timing drive roller 32a. For this reason, there is a possibility that the timing driving roller 32a is inadvertently moved with respect to the transfer cover 8, but at this time, the timing driving roller 32a is further moved beyond the movable range along with the paper conveyance guide 50. In such a case, an excessive load is applied to the paper transport guide 50, and the paper transport guide 50 may be damaged.

  Therefore, as shown in FIGS. 8A to 8D, a partial shape of the transfer cover 8, for example, a stopper surface 52 b is formed on the support member 52, and the rotating arm 45 is brought into contact with the stopper surface 52 b, so that The rotation arm 45 or the timing drive roller 32a cannot be moved carelessly. By adopting such a configuration, it is possible to reliably prevent the parts from being damaged.

(Positioning guide member)
On the other hand, as shown in FIG. 9, a timing driven roller 32b is disposed on the main body side. The timing driven roller 32b and the timing driving roller 32a on the transfer cover 8 side come into contact with each other to constitute a timing mechanism by the timing roller pair 32.

  Positioning guide members 55 for positioning the timing driving roller 32a with respect to the timing driven roller are arranged at both ends of the rotation shaft 32b1 of the timing driven roller 32b as shown in FIGS. As shown in FIG. 11, the guide member 55 has a shaft hole 55a into which the rotation shaft 32b1 of the timing driven roller 32b is fitted, and an upper jaw portion 55b and a lower jaw portion 55c that protrude horizontally toward the front, that is, the transfer cover 8 side. The lower jaw portion 55c protrudes longer than the upper jaw portion 55b, and an insertion port 55d opened obliquely upward is formed between both jaw portions 55b and 55c.

  Therefore, the insertion port 55d has a rake shape that smoothly receives the rotation shaft 32a1 of the timing drive roller 32a from obliquely above. This scooping shape is such that when the rotary shaft 32a1 of the timing drive roller 32a is lifted from the lower jaw 55c before reaching the depth of the positioning guide member 55, the rotary shaft 32a1 of the timing drive roller 32a interferes with the positioning guide member 55. There is also a function to prevent damage.

  An arcuate end 55e is formed on the opposite side of the insertion port 55d. At the final stage of closing the transfer cover 8, both ends of the rotating shaft 32a1 of the timing drive roller 32a proceed in the horizontal direction toward the arc-shaped end portion 55e. However, both ends of the rotating shaft 32a1 contact the arc-shaped end portion 55e at the maximum. It only progresses until just before touching. That is, a slight gap S3 remains between the rotation shaft 32a1 and the arcuate end 55e of the positioning guide member 55 with the transfer cover 8 completely closed.

  The gap S3 is necessary for forming a predetermined nip pressure of the timing roller pair 32. When the gap S3 becomes zero, the outer peripheral surface reference of the timing drive roller 32a becomes the arcuate end 55e, and the dimensional accuracy variations of a plurality of parts existing from the rotary shaft 32a1 to the outer peripheral surface of the roller 32a are accumulated, and the nip pressure Cause a large variation. Also, the nip pressure varies due to deterioration with time such as wear on the outer peripheral surface of the roller 32a. The problem can be avoided by leaving the gap S3.

  The lower jaw portion upper surface 55b1 of the positioning guide member 55 functions as a guide portion of the rotation shaft 32a1 of the timing drive roller 32a, and the rotation shaft 32a1 slides while being in pressure contact with the jaw portion upper surface 55b1. The lower jaw upper surface 55b1 is formed in a straight line so that a proper and precise nip portion is formed between the timing driven roller 32b and the timing driving roller 32a. Thereby, the variation in the positional relationship between the rotation shafts of the timing driven roller 32b and the timing driving roller 32a can be extremely reduced, and accurate timing performance and skew correction performance can be provided. Here, the “linear shape” does not mean only a complete straight line, but also includes a shape that approaches almost linearly toward the timing driven roller 32b.

  A guide member similar to the positioning guide member 55 is disposed in the vicinity of both ends of the rotation shaft of the driving roller 18 of the intermediate transfer belt 16 on the main body side, and the relative positioning accuracy between the transfer roller 20 and the driving roller 18 is determined. It can also be secured by a positioning guide member.

(Upstream end connection structure of paper transport guide)
As shown in FIG. 15, the upstream end of the paper transport guide 50 is a plurality of paper transport guides 53 disposed on the further upstream side of the paper transport guide 50 and disposed at predetermined intervals in the paper width direction. Are connected by a connection structure formed by a rectangular recess 53a and a plurality of rib-shaped protrusions 50c. In this embodiment, each recess 53a is formed at the downstream end of the upstream sheet conveyance guide 53, and each rib-shaped protrusion 50c is formed at the upstream end of the downstream sheet conveyance guide 50 so as to protrude toward the sheet conveyance path. ing. The shape of the convex portion 50c can be changed to another shape that is not a rib shape as long as the conveyance of the paper is not hindered.

  The rib-like convex portion 50c extends a predetermined length in the paper conveyance direction, and the tip (upstream end) extends a predetermined length further upstream than the upstream edge portion 50d of the paper conveyance guide 50. The tip of the rib-like convex portion 50c further extended from the edge portion 50d in this way has a predetermined size around the tip of the rib-like convex portion 50c (both sides and upstream) at the center in the width direction of the concave portion 53a. Inserted with a gap.

  As shown in the partially enlarged view of FIG. 15, the height of the tip of the rib-like convex portion 50c is set to coincide with the conveyance surface of the upstream-side sheet conveyance guide 53 in order to prevent the sheet from being caught. Slightly lower. On the surface of the paper conveyance guide 53, a rib-like convex portion 53b extending in the paper conveyance direction so as to terminate at the bottom of the concave portion 53a may be formed. Such a rib-like convex portion 53b provides an effect of smooth paper conveyance.

  The upstream sheet conveyance guide 53 is fixedly disposed on the transfer cover 8, and therefore, the downstream sheet conveyance guide 50 is interlocked with the movement of the timing drive roller 32a when the transfer cover 8 is opened and closed as will be described later. The two paper conveyance guides 50 and 53 may interfere with each other. Therefore, in this embodiment, as described above, the connection is made by the connection structure formed by the concave portion 53a and the rib-like convex portion 50c.

  As described above, with the connection structure formed by the concave portion 53a and the rib-like convex portion 50c, the two paper transport guides 50 and 53 are arranged as close as possible so as to be advantageous in the compact design of the apparatus. The downstream side paper conveyance guide 50 can be moved in conjunction with the timing drive roller 32a. In addition, since the tip of the rib-like convex portion 50c is inserted into the concave portion 53a of the paper conveyance guide 53, an effect that the paper is hardly caught at the joint between the paper conveyance guides 50 and 53 can be obtained.

  In the combination of the rib-like convex portion 50c and the concave portion 53a, the rib-like convex portion 50c may be disposed in the upstream side paper conveyance guide 53 and the concave portion 53a may be formed in the downstream side paper conveyance guide 50, contrary to the above. Alternatively, the meshing of the rib-like convex portions 50c and the concave portions 53a may be alternately reversed in the paper width direction.

(Protection part for electrical components)
In the embodiment of the present invention, as described above, the timing driving roller 32a is moved as shown in FIGS. 12A to 12C in accordance with the opening and closing of the transfer cover 8, so that the following new problem arises. That is, when the transfer cover 8 is closed, the space between the timing drive roller 32a and the transfer roller 20 is not so much opened as shown in FIG. 16A, but when the transfer cover 8 is opened, the timing drive roller 32a is self-weighted as shown in FIG. 16B. Is lowered in the direction of the arrow, and a relatively large space is formed on the downstream side (upper side in FIG. 16B) (the rotation arm 45 and the like are not shown in FIGS. 16A and 16B). The inner surface of the transfer cover 8 is exposed through this space.

  Since various electrical components are usually disposed on the exposed inner surface of the transfer cover 8, the electrical components are exposed when the transfer cover 8 is opened. For this reason, when the user opens the transfer cover 8 for jam processing, there is a possibility that the electrical component may be touched unexpectedly and damaged. Therefore, in this embodiment, the rectangular plate-shaped protection portion 54 that covers the electrical component is disposed so as to protrude from the transfer cover 8. Thus, when the transfer cover 8 is opened and the jam processing is performed, there is no possibility that the user accidentally touches the electrical component and damages the electrical component.

(Opening / closing of the transfer cover and operation of the timing drive roller)
12A to 12C sequentially show the final stage when the transfer cover 8 is closed. FIG. 12A shows a state immediately before the rotation shaft 32a1 of the timing drive roller 32a comes into contact with the positioning guide member 55. FIG. The positional relationship of the timing drive roller 32a and the like with respect to the transfer cover 8 is exactly the same from the state where the transfer cover 8 is completely opened as shown in FIGS. 3 and 4 to FIG. 12A, and there is no change in the positional relationship therebetween. .

  When the transfer cover 8 is rotated, the body-side component is within the range of the arcuate movement locus (for example, the movement locus A1 of the timing drive roller 32a shown in FIG. 12A) drawn by the secondary transfer roller 20 and the timing drive roller 32a. It cannot be installed. Examples of the main body side components that may interfere with the secondary transfer roller 20 and the timing drive roller 32a include the fixing device 34 shown in FIGS. 2 and 4 and the intermediate transfer belt 16 (photosensitive drum in the case of a monochrome image forming apparatus). And its driving roller 18.

  In recent image forming apparatuses, there is an increasing need for a layout in which a timing roller pair is disposed close to the lower side of the end portion of the intermediate transfer belt and a photosensitive drum as an image carrier for compactness. In the case of such a compact layout, there is an increased possibility that the arcuate movement locus A1 of the timing drive roller 32a interferes with the intermediate transfer belt 16 and the drive roller 18. That is, when the transfer cover 8 is opened and closed, the movement locus A1 of the timing drive roller 32a is likely to interfere with the intermediate transfer belt 16 and the drive roller 18. In particular, when the timing roller pair 32 is disposed slightly behind the transfer nip portion of the intermediate transfer belt 16 because of the sheet conveyance path, the possibility of interference becomes even more remarkable.

  Further, in order to make the apparatus main body compact, it is necessary to shorten the height in the vertical direction. When such shortening is performed, the distance from the rotating shaft 12 of the transfer cover 8 to the timing driving roller 32a. The turning radius R1 is shortened. Then, the movement locus A1 of the timing drive roller 32a is closer to the intermediate transfer belt 16, and this movement locus of the timing drive roller 32a becomes an obstacle to shortening the height of the apparatus main body.

  In the embodiment of the present invention, as shown in FIG. 2, the timing roller pair 32 is disposed immediately below and behind (on the left side) of the driving roller 18 of the secondary transfer belt 16 to be compact in both the vertical direction and the depth direction of the apparatus. 12A to 12C, FIG. 13 and the following description, the movement locus A1 of the timing drive roller 32a is set to avoid the secondary transfer belt 16 and the drive roller 18.

  In the state of FIG. 12A, the rotating arm 45 abuts against the stopper surface 52 b of the support member 52 with its own weight, while the pressure lever 46 abuts against the stopper 48 with the force of the tension spring 47. A gap S <b> 2 is formed between the rotating arm 45 and the pressure lever 46, that is, between the pressing surface 46 c of the pressing lever 46 shown in FIG. 6 and the pressed surface portion 45 c of the rotating arm 45. Accordingly, the pivot arm 45 and the timing drive roller 32a are movable rightward and upward within the range allowed by the gap S2 from the state shown in FIG. 12A.

  However, when the transfer cover 8 is rotated in the opening direction (clockwise) about the rotation shaft 12 from the state of FIG. 12A, the rotation arm 45 is inclined downward to the stopper surface 52b at the upper end of the support member 52. It slides to the support shaft 27a side with its own weight while being in contact. As a result, the protrusion amount of the timing drive roller 32a toward the inner surface side of the transfer cover 8 is reduced, and there is a possibility that the user may accidentally touch the timing drive roller 32a when the user opens the transfer cover 8 during paper jam processing or the like. Can be reduced.

  Further, the position at which the rotating arm 45 is moved to the support shaft 27 a by its own weight is at least until the rotating arm 45 comes into contact with the stopper surface 52 b at the upper end of the support member 52 when the transfer cover 8 is closed. Is maintained. Therefore, as described above, the non-interference area between the timing drive roller 32a and the main body-side component can be secured as much as the protrusion amount of the timing drive roller 32a is reduced by the movement due to its own weight.

  FIG. 12B shows a state immediately before the transfer cover 8 is completely closed. This state is a moment when the rotation shaft 32a1 of the timing driving roller 32a comes into contact with the upper surface 55c1 of the lower jaw portion 55c of the positioning guide member 55, whereby the rotating arm 45 starts to float from the support member 52.

  Even in this state, the gap 2 still remains between the rotating arm 45 and the pressure lever 46, and the force of the tension spring 47 is received by the stopper 48, and the force of the tension spring 47 is applied to the rotation arm 45. It is not working. Therefore, even if the transfer cover 8 is further closed from the state shown in FIG. 12B, the rotating arm 45 can freely rotate in the clockwise direction (the direction of lifting from the support member 52) until the gap S2 becomes zero. It is in a state.

  When the transfer cover 8 is further closed from the state shown in FIG. 12B, the rotation shaft 32a1 of the timing drive roller 32a is supported on the lower jaw upper surface 55c1 of the positioning guide member 55, and the height thereof becomes constant. The height of the support shaft 27a further decreases as the transfer cover 8 is closed. As a result, the turning arm 45 gradually turns clockwise about the support shaft 27a.

  Then, when the clearance S <b> 2 becomes zero and the rotating arm 45 contacts the pressure lever 46, the urging force of the tension spring 47 acts on the pressure lever 46. That is, at the same time as the rotating arm 45 abuts against the pressure lever 46, the pressure lever 46 is separated from the stopper 48 to form a gap S 1 therebetween, and the urging force of the tension spring 47 is applied to the tip of the pressure lever 46. The pressure is transmitted from the pressing surface 46 c to the pressed surface portion 45 c of the rotating arm 45.

  12C shows a state in which the transfer cover 8 is completely closed (the inner surface of the transfer cover 8 is shown in FIG. 16B). In this state, the urging force of the tension spring 47 is transmitted to the rotating arm 45 via the pressure lever 46. Then, the rotation arm 45 is urged to rotate counterclockwise about the support shaft 27a. Since the rotation shaft 32a1 of the timing drive roller 32a is guided in the horizontal direction along the lower jaw upper surface 55c1 of the positioning guide member 55 (not shown in FIG. 12C), the rotation drive force of the timing drive roller 32a The rotation shaft 32a1 is actually shifted and biased in a direction in which it approaches linearly toward the rotation shaft 32b1 of the timing driven roller 32b (a direction away from the support shaft 27a). Accordingly, the support shaft 27a of the rotation arm 45 moves relatively to the right end in the elongated hole 45a in FIG. 12C, and the rotation arm 45 moves radially outward about the support shaft 27a and the rotation shaft 12 of the transfer cover 8. It will be in the state extended to the maximum.

  In this state, the timing driving roller 32a comes into contact with the timing driven roller 32b, and a nip portion is formed between the two rollers to constitute a timing mechanism by the timing roller pair 32. Further, the transfer roller 20 contacts the drive roller 18 of the intermediate transfer belt 16 through the intermediate transfer belt 16 by the urging force of the compression spring 25, and the end of the transfer roller 20 and the end of the intermediate transfer belt 16 supported by the drive roller 18. A predetermined transfer nip pressure is formed between the two portions.

  By the way, after the rotation shaft 32a1 of the timing driving roller 32a abuts the lower jaw upper surface 55c1 of the positioning guide member 55, the rotation shaft 32a1 is always kept in contact with the lower jaw upper surface 55c1 until the timing mechanism is configured as described above. To do. In this regard, the roller positioning mechanism of Patent Document 2 is configured to guide the roller shaft with the guide groove of the guide guide formed by the upper and lower jaws on the main body side. However, the biasing direction of the spring biasing the roller is It matches with the guide groove direction.

  In such a roller urging mechanism, it is unclear whether the roller shaft is guided by the upper or lower jaw, and there is a possibility that the final positioning position of the roller may not be determined based on the upper jaw reference or the lower jaw reference. In the embodiment of the present invention, the rotating shaft 32a1 of the timing drive roller 32a is guided by the lower jaw upper surface 55c1 to the end constituting the timing mechanism, so that there is no such problem.

  Further, since the embodiment of the present invention is configured to transmit the urging force of the tension spring 47 to the rotating arm 45 via the pressure lever 46, the elongated hole 45a simultaneously urges the rotating arm 45 to rotate counterclockwise. As described above, the biasing force of the tension spring 47 can also be used for forming the nip pressure of the timing roller pair 32 while enabling positioning based on the lower jaw upper surface 55c1. It is possible. In this respect, the roller urging structure as in Patent Document 2 has a problem that the positioning of the roller becomes unstable as described above even if the nip pressure form by the spring is possible.

  In the timing mechanism using the timing roller pair 32, the mechanism for determining the position of the timing driving roller 32a relative to the timing driven roller 32b is the lower jaw upper surface 55c1 of the guide member 55 and the rotation shaft 32a1 of the timing driving roller 32a guided by this. And the outer peripheral surface of the timing drive roller 32a itself. Even if the base end side of the rotating arm 45 is rattled by a gap existing between the support shaft 27a and the elongated hole 45a, the position of the timing driving roller 32a is not affected.

  Such a positioning mechanism is simple and space-saving compared with the positioning mechanism of the cited reference 1. In addition, since the outer peripheral surface of the timing driving roller 32a is positioned in a state of being linearly urged toward the outer peripheral surface of the other timing driven roller 32b, the components of the timing driving roller 32a are as described above. The nip pressure does not fluctuate even if there is aging deterioration such as variations in dimensional accuracy and wear on the outer peripheral surface of the roller 32a.

  The timing driving roller 32a receives the reaction force of the nip portion from the timing driven roller 32b, and the rotation arm 45 is pushed back in the clockwise direction in the longitudinal direction by the reaction force. On the other hand, the reaction force of the nip portion is transmitted to the pressing surface 46c of the pressure lever 46 via the rotating arm 45, whereby the pressure spring 46 is pushed back slightly in the clockwise direction, so that the tension spring 47 is slightly stretched. It is. At this time, a gap S1 remains between the pressure lever 46 and the stopper 48, and the urging force of the tension spring 47 changes the lever ratio of the pressure lever 46 (the distance from the hooking portion 46b of the tension spring 47 to the support shaft 27b). The ratio of the distance from the support shaft 27b to the pressing surface 46c) is reflected in the nip pressure.

  The final stage when the transfer cover 8 is closed has been described in order with reference to FIGS. 12A to 12C. Next, the movement trajectory of the timing drive roller 32a when the transfer cover 8 is opened and closed will be described with reference to FIGS. A description will be given based on (C). FIGS. 13A to 13C correspond to FIGS. 12A to 12C, respectively, and reference numeral 12 in the drawing denotes the rotating shaft 12 of the transfer cover 8 shown in FIG. However, the actual movement locus of the timing drive roller 32a is the movement locus (rotation locus) A1 in FIG. 13A, and the movement locus A2 and A3 in FIGS. 13B and 13C are the intermediate transfer belt 16 and the drive roller. 18 is a hypothetical one for explaining the interference relationship with 18.

In FIG. 13A, as described above, the rotating arm 45 remains in contact with the stopper surface 52b of the support member 52 by its own weight, and when the transfer cover 8 is opened and closed, the state shown in FIG. The outer peripheral surface of the timing drive roller 32a draws a rotation locus, that is, a movement locus A1 around the rotation shaft 12. The radius R1 of the moving locus A1 is L1 ₁ + D1 / 2 (L1: length from the rotating shaft 12 to the center of the rotating shaft 32a1 of the timing driving roller 32a, D1: diameter of the timing driving roller 32a). In contrast, the intermediate transfer belt 16 on the main body side and the driving roller 18 are arranged so as not to interfere with each other. That is, the relationship is L1 ₁ + D1 / 2 <L2-D2 / 2 (L2: length from the rotating shaft 12 to the center of the rotating shaft 32b1 of the timing driven roller 32b, D2: diameter of the timing driven roller 32b).

  On the other hand, the transfer roller 20 is already in contact with the drive roller 18 of the intermediate transfer belt 16 in FIG. 13A, and when the transfer cover 8 is further closed, the transfer roller 20 and the transfer roller 20 are maintained in this contact state. The compression spring 25 (see FIGS. 2 and 4) between the cover 8 and the cover 8 is compressed.

Next, and FIG. 13 (B) and FIG. 13 (C) the length of the L1 ₁ sequentially shortened as _{L1 1 → L1 2 → L1 3} (L1 3 <L1 2 <L1 1). This is because when the rotation shaft 32a1 of the timing drive roller 32a abuts on the upper surface 55c1 of the lower jaw portion 55c of the positioning guide member 55, the rotating arm 45 supporting the timing drive roller 32a rotates clockwise about the support shaft 27a. (See FIGS. 12B and 12C). As a result, the radius R2 of the movement locus A2 becomes L1 ₂ + D1 / 2 in FIG. 13B (L1 ₂ <L1 ₁ ), and the radius R3 of the movement locus A3 becomes L1 ₃ + D1 / 2 in FIG. 13C. (L1 ₂ <L1 ₁ ).

  Here, from the state shown in FIG. 13C, when the timing driving roller 32a is rotated in the clockwise direction around the rotating shaft 12, that is, the rotating arm 45 is rotated with respect to the end plate 27 or the transfer cover 8. It is assumed that the transfer cover 8 is opened without making it. This assumption is for confirming the degree of interference with the main body side component when the rotation shaft of the roller is fixedly disposed on the transfer cover as in Patent Document 3.

In this case, the timing drive roller 32a interferes with the end of the intermediate transfer belt 16 on the main body side, as indicated by a movement locus A3 in FIG. The radius R3 of the movement locus A3 at this time is L1 ₃ + D1 / 2, and the relationship is L1 ₃ + D1 / 2> L2-D2 / 2.

That is, the magnitude relationship of the inequality sign is reversed from that in FIGS. 13A and 13B. In other words, in this embodiment, at least the movement locus A3 covers the drive roller 18 as compared with the apparatus of Patent Document 3. This shows that it can be made more compact as much as possible. Compared with FIG. 13A (FIG. 12A), the rotating arm 45 rotates in the clockwise direction with respect to the end plate 27, and the rotating arm 45 biases the pressing lever 46 or the tension spring 47. This is because the radius R3 of the movement locus A3 is longer than the radius R1 = L1 ₁ + D1 / 2 of the movement locus A1 in FIG. 13A as a result of moving in a direction away from the support shaft 27a.

  In this embodiment, when the transfer cover 8 is being opened and closed and the timing drive roller 32a passes near the main body side component (the intermediate transfer belt 16 and its drive roller 18), the rotating arm 45 is counteracted by its own weight. The support member 52 is abutted against the stopper surface 52b by rotating clockwise. By doing so, the radius R1 of the movement trajectory A1 can be shortened and interference with the main body side parts can be avoided.

Even if the rotation arm 45 temporarily lifts from the stopper surface 52b of the support member 52 due to an impact or the like while the transfer cover 8 is opened or closed, the rotation arm 45 is moved to the stopper 48 as shown in FIGS. 13B and 12B. The lifting height is regulated by the pressure lever 46 that is in contact. Due to this height restriction, the radius R2 of the movement locus A2 of the timing driving roller 32a is at most L1 ₂ + D1 / 2 as shown in FIG. 13B, and the timing driving roller 32a is connected to the intermediate transfer belt 16 and the driving roller 18. There is no risk of interference.

  However, with the movement locus A1, the timing driving roller 32a cannot be brought into contact with the timing driven roller 32b on the main body side even when the transfer cover 8 is closed to the end. Therefore, after the timing drive roller 32a passes through the intermediate transfer belt 16 and the drive roller 18 and moves to the lower side, the rotation shaft 32a1 of the timing drive roller 32a is moved to the upper surface 55c1 of the lower jaw portion 55c of the positioning guide member 55. The rotating arm 45 is rotated clockwise by this contact. At the same time, the rotating arm 45 is moved away from the support shaft 27 a by the urging force of the pressure lever 46 or the tension spring 47.

  By moving the timing drive roller 32a as described above while the transfer cover 8 is opened and closed, the timing drive roller 32a is disposed below the end of the intermediate transfer belt 16, that is, immediately below the drive roller 18 and on the back side (left side). Layout becomes possible. This layout makes it possible to shorten both the depth and the vertical height of the apparatus, and promote the downsizing of the apparatus.

  FIG. 17 shows a modification of the present invention. Instead of rotating the transfer cover 8, the transfer cover 8 is opened by sliding horizontally along a horizontal rail 66 arranged at the lower part of the apparatus. ing. A method of opening and closing the transfer cover 8 in the horizontal direction as described above is known as shown in FIG. However, in the horizontal opening / closing system, the transfer roller 20 and the timing driving roller 32a on the transfer cover 8 side are less likely to interfere with the main body side parts as the apparatus is reduced in size and space. The positioning accuracy of the drive roller 32a and the influence of the friction that the intermediate transfer belt 16 receives from the transfer roller 20 are problems.

  According to the embodiment of the present invention, the transfer roller 20 and the timing drive roller 32 a can be accurately positioned at the final position by using the positioning guide member 55. Further, the final position of the positioning guide member 55 can be raised with respect to the horizontal movement height depending on the guide shape of the positioning guide member 55, which makes it possible to lower the arrangement of the body-side parts on the way and to make the apparatus compact. Can be promoted.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the embodiments are examples in which the present invention is applied to an image forming apparatus. Of course, the present invention can be applied to other than the image forming apparatus. In the above embodiment, the timing driven roller 32b, the intermediate transfer belt 16 and the driving roller 18 are disposed as the main body side feeding member, and the timing driving roller 32a and the secondary transfer roller 20 are disposed as the cover side feeding member. May be a roller or an endless belt or the like instead of the roller.

  The type of the feed member is arbitrary, and may be a feed member other than the timing feed member or the transfer feed member. For example, the pressure roller 34b of the fixing device 34 is disposed on the transfer cover 8 so that the position of the pressure roller 34b can be changed. Then, this may be moved by the main body side guide member so as to avoid interference with the main body side parts in the vicinity of the main body side fixing roller 34a. The direction of movement by the guide member is, for example, when the direction crossing the opening / closing locus of the cover is the first direction and the direction of separating the second direction is the direction of approaching the main body side feeding member. It can be moved in the first direction by the closing operation and moved in the second direction by the opening operation.

  Furthermore, in the above-described embodiment, the sheet conveyance guide 50 on the upstream side of the timing driving roller 32a is engaged with the rotation shaft 32a1 of the timing driving roller 32a. A configuration is possible in which the sheet conveyance guide is provided on the upstream side or downstream side of the member so that the position of the sheet conveyance guide can be changed, and the downstream end or the upstream end of the sheet conveyance guide is engaged with the feeding member. In that case, the upstream end or the downstream end of the sheet conveying guide on the side not engaged with the feeding member can be slidably engaged with the engaging portion on the cover side as necessary.

  In the embodiment, the timing driving roller 32 a is guided by the guide member 55, but the secondary transfer roller 20 can be guided by a guide member equivalent to the guide member 55. Further, although the number of feeding members on the main body side and the cover side is two in the embodiment, it may be one or two or more.

  Further, the arrangement relationship between the timing driving roller 32a and the timing driven roller 32b may be reversed such that the timing driving roller 32a is arranged on the main body side and the timing driven roller 32b is arranged on the transfer cover 8.

  The present invention can also be applied to a monochrome image forming apparatus that does not use the intermediate transfer belt 16. In this case, a photosensitive drum is disposed as an image carrier instead of the intermediate transfer belt 16, and the photosensitive drum is disposed on the outer peripheral surface of the photosensitive drum. Press the transfer roller on the transfer cover side.

  In the above embodiment, the transfer cover 8 has been described as having the duplex unit 9, but the transfer cover 8 without the duplex unit may be used.

1K, 1Y, 1M, 1C Process unit 2K, 2Y, 2M, 2C Image carrier (photosensitive drum)
8 Transfer cover 9 Double-side unit 9a Conveying housing 9b Return path 12 Transfer cover rotating shaft 15 Transfer device 16 Intermediate transfer belt 17 Driven roller 18 Secondary transfer drive rollers 19K, 19Y, 19M, 19C Primary transfer roller 20 Secondary transfer roller 20a Rotating shaft 25 Compression spring 27 End plate 27a Support shaft 30 Support plate 30 Paper feed tray 30a Paper feed roller 31 Paper feed path 32 Timing roller pair 32a Timing drive roller 32b Timing driven roller 33 Post transfer transfer path 34 Fixing device 34a Fixing roller 34b Pressure roller 36 Paper discharge path 37 Paper discharge roller pair 41 Reverse conveyance path 45 Rotating arm 46 Pressure lever 47 Tension spring (biasing means)
50 Paper conveyance guide 52 Support member 52a Longitudinal groove 52b Stopper surface 55 Guide member 65 Compression spring 66 Horizontal rail A1 Movement path of timing drive roller

JP 2011-85815 A JP 2004-20574 A JP 2000-231321 A (Patent No. 3670153) JP 2002-127528 A

Claims (12)

A paper transport device having one or more pairs of rollers for transporting with a paper sandwiched along a paper transport path,
A cover disposed on the side surface of the apparatus main body so as to be able to open and close a part of the paper transport path so as to be rotatable outward about a rotation axis parallel to the axis of the pair of rollers ;
A body-side roller arranged on the body side a one of a pair of the rollers,
A cover-side roller that is repositionable disposed with respect to said cover an other pair of said rollers,
A guide member that is disposed on the main body side and guides the cover-side roller as the cover opens and closes;
Is repositionable disposed upstream or downstream of the cover-side roller, operatively in a engaged with the sheet conveying guide on the cover side roller and the cover-side roller, the downstream end of the paper conveying guide Alternatively, a paper transport guide having an upstream end engaged with the cover side roller and an end on the opposite side of the paper transport guide slidably engaged with an engagement portion formed on the cover ;
Have

When the guide member has a first direction as a direction approaching the main body side roller in a direction crossing the opening / closing locus of the cover with the rotation axis as a center, and a second direction as a direction away from the main body side roller , the cover side roller Is moved in the first direction by the closing operation of the cover and is moved in the second direction by the opening operation. 2. The sheet conveying apparatus according to claim 1 , wherein the engaging portion of the cover is formed on the sheet conveying path side when viewed from the opposite end of the sheet conveying guide serving as the engaged portion of the engaging portion. 2. The paper transport according to claim 1 , wherein the engaging portion of the cover is formed on the side opposite to the paper transporting path side when viewed from the opposite end of the paper transporting guide serving as the engaged portion of the engaging portion. apparatus. The engagement portion of the cover is located on both sides of the paper conveyance path side and the opposite side of the paper conveyance path side when viewed from the opposite end of the paper conveyance guide serving as the engagement portion of the engagement portion. the paper conveying apparatus of claim 1 formed of a pair. The engagement portion, the main body-side roller and any one of the sheet conveying device of the cover-side roller in claim 1 which extend in the feeding direction of the sheet sandwiched 4. Urges the body side roller by an urging means in a state in which the cover-side roller closing the cover, from claim 1, the engaging portion has extended perpendicularly to the biasing direction by the biasing means Any one of 4 paper conveyance apparatuses. At either one of the end portion of the paper conveyance guide to be engaged with the engagement portion of the cover and the end portion of the other paper conveyance guide adjacent to the end portion, and forming a plurality of protrusions for guiding the sheet, the other to the end, any one of the paper conveying apparatus of claim 1 in which a recess in which the protrusion is inserted 6. The roller is a roller, the paper transport guides, rotatably engaged with any one of the paper conveying apparatus of claims 1 7 to the rotation axis of the roller. The required part of the hidden part is covered with a protective portion in a state where the hidden part on the back side of the cover-side roller or the paper transport guide appears on the inner surface of the cover by opening the cover. Item 9. The paper conveyance device according to any one of Items 1 to 8 . A bearing portion that can be engaged with the rotation shaft of the roller that is the cover side roller is formed in the paper conveyance guide, and a notch portion that can receive the rotation shaft from the radial direction is formed in a part of the bearing portion. 9. A paper conveying apparatus according to claim 8 . A writing unit that writes image information, an image forming unit that forms an image based on the image information of the writing unit, a transfer unit that transfers an image formed by the image forming unit to a sheet, and the transferred image on a sheet a fixing unit for fixing said an image forming apparatus having a sheet conveying path for conveying via said fixing portion from the transfer section to a discharge portion of the paper, of the claims 1 to 10 in the sheet transport path An image forming apparatus provided with any one of the sheet conveying apparatuses. 12. The image forming apparatus according to claim 11 , wherein the image forming apparatus is configured as a complex machine in which two or more of a copying machine, a printer, and a facsimile machine are combined.